This invention relates to the manufacture and construction of roofing panels for residential, light commercial, commercial and industrial building construction.
One popular type of home is what is considered in the construction industry a timber frame home. Timber frame homes are constructed of a plurality of heavy timber frame members and are designed so as to expose the timbers of the frame inside the home.
Traditionally a conventional light frame was built around or between the timber frame members, a layer of drywall secured to the inside surfaces of the light frame members, fiberglass insulation inserted between the light frame members, and then covered on the outside with siding. However, this method of construction was slow, labor intensive and costly. In addition, the resulting building or structure was not energy efficient because the insulation was interrupted every 16 or 24 inches, for example, by a light frame member (stud) or rafter allowing heat to easily escape and cold to enter the building at these points.
In the 1970""s, structural insulating panels, commonly known in the industry as stress-skin panels, were developed for use in the residential construction of timber frame homes. The stress-skin panels are nailed to the exterior of the timber frame members leaving the frame exposed inside the home, thus creating an attractive appearance. These stress-skin panels used in conjunction with a timber frame replaced in many applications the standard 2xc3x974 construction of homes. The stress-skin panels were considered stronger than 2xc3x974s and were considered to provide better insulating capability.
A stress-skin panel is a panel comprising an outer skin, an inner skin and several inches of rigid foam insulation sandwiched between the two layers of sturdy sheathing material or skins. The outer and inner skins may be constructed of a plurality of materials, but are usually made of plywood, waferboard or oriented strand board (OSB). The foam insulation core located between the two skins is expanded polystyrene (commonly called EPS) or urethane foam, typically 3 xc2xdxe2x80x3 thick. These panels are typically prefabricated before being installed as part of the walls and roofs of structures like homes, commercial offices, etc.
Because both plywood and OSB are commercially available only in certain size sheets, the size of the stress skin panels is limited. For example, plywood is typically available in 4xe2x80x2xc3x978xe2x80x2 sheets while OSB is typically available in larger size sheets (up to 8xe2x80x2xc3x9724xe2x80x2). Therefore, the size of the stress-skin panels is limited to between 4xe2x80x2xc3x978xe2x80x2 and 8xe2x80x2xc3x9724xe2x80x2. Due to the limited size of the stress-skin panels, a large number of panels must be used in order to completely construct a roof or the perimeter walls of a building. Additionally, due to the weight of the stress-skin panels, a crane is often required to lift the stress-skin panels into place, particularly when the stress-skin panels are used to construct a roof. The relatively large number of stress-skin panels necessary to construct such a roof requires a large number of individual laborers and additionally requires a large amount of crane time (time that the crane is in use). Both of these requirements increase the cost of constructing a timber frame building using stress skin panels.
Stress-skin panels are manufactured by injecting a liquid urethane between the two skins and allowing the liquid urethane to expand between the skins, the urethane foam adhering to the inner surfaces of the skins without any other adhesives. Alternatively, if the foam insulation is EPS, the foam insulation is glued or adhesively secured to the outer sheathing layers or skins with a urethane glue. With either type of insulation, over time the adhesive or bond used to secure the foam insulation to the two skins of the panel may deteriorate if exposed to extreme temperature fluctuations causing the inner and outer skins of the panel to sheer apart from the foam insulation.
In addition, some type of sealant must be inserted along the joints between adjacent stress-skin panels in order to reduce air and moisture flow through these joints. Alternatively, thin horizontal splines may be used between panels to minimize thermal breaks. Improperly sealed joints or seams can allow moisture to collect and the trapped moisture can eventually cause the materials of the stress-skin panels to swell and deteriorate.
These stress-skin panels are secured to the heavy timber frame of a structure with long nails or screws known in the industry as pole, barn spikes or deck screws. The length of these nails or screws must be greater than the depth of the stress-skin panels so that the panels may be secured to the exterior surfaces of the timber frame members of the structure, the nails or screws passing through the entire stress-skin panel and into the timber frame members.
In cold climates where a large temperature differential exists between the exterior surface of panels and the interior of the structure, the nails or screws running through the panels may conduct heat and may cause condensation at the heads of the nails or screws. Over time, this condensation may cause the exterior layer of the stress-skin panels to rot which may eventually cause structural failure of the panels.
In addition, utilizing stress-skin panels to construct a timber frame home is expensive. Because the interior layers or skins of the stress-skin panels are visible from inside the building, another layer of material such as drywall or wood paneling is typically placed over and attached to the inner layer or skin of the stress-skin panels in order to make the inner surfaces of the panels aesthetically pleasing. Similarly, a layer of siding or other material is usually placed over the outer skins of the stress-skin panels.
If conventional stress-skin panels are used to construct the roof of a building, asphalt-saturated felt (known in the industry as tar paper) is applied in layers over the outer skins of the stress-skin panels and roofing material such as shingles attached directly to the outer skins of the panels. A roof constructed in such a manner does not vent properly. Due to excessive heat buildup between the roofing materials and the stress-skin panels due to the insulation inside the panels, the stress-skin panels may deteriorate. Hence, the useful life of a roof constructed of stress-skin panels is limited.
One prefabricated roof panel which attempts to better ventilate a roof made from a plurality of panels is disclosed in U.S. Pat. No. 4,852,314. This patent discloses a generally planar deck spaced above a stress-skin panel by a plurality of spaced spacers between which air may flow up the roof and escape. The roofing panels disclosed in this patent have a substrate of rigid foam material sandwiched between two facer boards made of fiberglass. Conventional roofing materials such as asphalt-saturated felt and asphalt shingles are secured to the substantially planar deck portion of the panels. Although the roofing panels disclosed in this patent do provide ventilation, the panels are limited in size to the standard sizes of sheets of plywood or OSB. Additionally, these roofing panels must be attached to the rafters of a roof with nails or screws of a length greater than the depth of the panels. Therefore, the utility and longevity of such roofing panels are limited for the reasons described above.
In light of the aforementioned drawbacks of using stress-skin panels to construct the roof of a building, a need exists for a roofing panel which is structurally sounder than stress-skin panels and will not deteriorate or degrade over time due to seasonal temperature fluctuations. A need also exists for a roofing panel which may be made of a larger size than the size of one sheet of plywood or OSB so that the roof of a building may be constructed of a lesser number of panels than has heretofore been possible. Also, a need exists for a roofing panel which does not require the use of fasteners or nails of a length greater than the depth of the panel in order to secure the panel to timber frame members such as rafters, purlins, plates or other timber frame members.
Therefore, it has been one objective of the present invention to provide an insulated roof panel less susceptible to degradation over time than stress-skin panels.
It has been a further objective of the present invention to provide an insulated roof panel which does not require long fasteners to pass entirely through the panel in order to secure the panel to the timber frame members of a building.
It has been a further objective of the present invention to provide an insulated roof panel which may span greater distances than stress-skin panels.
It has been a further objective of the present invention to provide an insulated roof panel which may be customized for particular applications.
The invention of this application which accomplishes these objectives comprises an insulated roof panel having a longitudinal dimension and a transverse dimension. The longitudinal dimension is preferably greater than the transverse dimension, so the insulated roof panel is generally rectangular. However, the insulated roof panel may be square as well. Additionally, the insulated roof panel has a top surface and bottom surface, the distance between the top and bottom surfaces of the insulated roof panel defining the thickness of the insulated roof panel.
One embodiment of the insulated roof panel of the present invention comprises a plurality of longitudinally extending web trusses or spanners built into the insulated roof panel. Each of these web trusses comprises at least one top cord, a bottom cord spaced from the top cord or cords and a plurality of webs joining the cords together. The webs are oriented such that they form an acute angle with the top and bottom cords which are parallel to one another.
Each web truss forming a part of the insulated roof panel has a top cord, a bottom cord and a plurality of webs joining the top and bottom cords. In another embodiment of the present invention, each insulated roof panel has a plurality of web trusses configured differently than those described above. Each of these web trusses has a pair of spaced parallel top cords, a bottom cord spaced from the top cords and a plurality of webs joining the bottom cord to the top cords. Although two different configurations of web trusses are illustrated and described in this application, other configurations of web trusses may be incorporated into the roof panel without departing from the spirit of the present invention.
The insulated roof panel of the present invention further comprises an inner sheathing secured to the lower surfaces of the bottom cords of the web trusses and an outer sheathing secured to the top surfaces of the top cords of the web trusses. The bottom surface of the inner sheathing comprises the bottom surface of the insulated roof panel, and similarly the top surface of the outer sheathing comprises the top surface of the insulated roof panel. The inner sheathing is preferably made of several pieces of tongue and groove finished wooden panels joined together but may be made of other materials such as gypsum wall board having a preapplied finish. Once the insulated roof panels of the present invention are secured to the rafters, purlins or other timber frame members of a timber frame building, the inner sheathing will be visible to persons inside the building and therefore preferably is aesthetically pleasing, particularly if the building is a residential home.
On the other hand, the outer sheathing of the insulated roof panel of the present invention is not visible to persons inside the building. The outer sheathing is preferably plywood, OSB or any other type of corrugated roof decking material but may be any other material. Conventional roofing materials such as asphalt-saturated felt and asphalt shingles are secured to the outer sheathing in order to complete the roof.
A vapor barrier preferably comprising a sheet of plastic extends the full transverse and longitudinal dimensions of the insulated roof panel and is sandwiched between the bottom cords of the web trusses and the inner sheathing. The vapor barrier is generally planar. However, the vapor barrier may additionally be wrapped around a pair of outermost web trusses, an insulation dam or other structure and secured thereto. The vapor barrier is impervious to moisture, and thus functions to protect the interior of the insulated roof panel of the present invention, and more particularly the insulation located inside the insulated roof panel.
A layer of insulation is located between the vapor barrier and the outer sheathing. The layer of insulation has a top surface which is preferably covered with a mesh member spaced from the outer sheathing in order to allow air to flow over the insulation and ventilate the insulated roof panel. The insulation may be any type of insulation, but is preferably non-rigid insulation which does not require the use of urethane glues or other environmentally harmful products.
An insulation dam extends at least partially around the perimeter of the roof panel and confines the insulation. The insulation dam comprises a pair of opposed longitudinally extending side dam members and a pair of opposed transversely extending end dam members which define a cavity in which the insulation is located. The insulation dam is preferably made of four individual planar members, the side dam members of the insulation dam being secured to the outermost web trusses of the insulated roof panel. However, the insulation dam may be a unitary rectangular member or a pair of L-shaped members.
The insulation dam contains the insulation but still allows air to flow over the top of the insulation and through the panel to properly vent the roof panel. The height of at least two of the insulation dam members is less than the height of the insulated roof panel and preferably equal to the distance from the inner sheathing to the top surface of the insulation. Thus a gap exists between the outer sheathing and the top surface of the insulation dam members, allowing air to flow over the insulation and vent moisture away from the insulation.
One embodiment of the insulated roof panel of the present invention has a plurality of hollow sleeves extending through the insulated roof panel. The hollow sleeves enable fasteners of a lesser length than the height of the insulated roof panel to be used to secure the insulated roof panel to the timber frame members. Because the shorter fasteners do not extend entirely through the insulated roof panels, thermal conductivity through the fasteners is limited. Therefore condensation does not occur at the heads of the fasteners causing deterioration of the outer sheathing of the roof panels as with stress skin panels. Consequently, the useful life of the roof panels is prolonged.
In one embodiment of the present invention, a pair or more of spaced brackets are used to secure each web truss to the timber frame members of the building. Each bracket extends over the bottom cord of one of the web trusses of the insulated roof panel and has a pair of holes therethrough. Above each bracket hole is a hollow sleeve extending downwardly from the upper surface of the insulated roof panel. Each hollow sleeve has two open ends and is adapted to allow a fastener to pass through the hollow sleeve. In order to secure the web truss to the timber frame members, each fastener is passed through one of the hollow sleeves, through one of the bracket holes and through the inner sheathing before entering one of the timber frame members. Once the fastener has passed through the hollow sleeve and into the timber frame member so that the head of the fastener is contacting the bracket, the sleeve is filled with insulation and plugged.
In an alternative embodiment of the present invention brackets are not used to secure the roof panel to the timber frame members. In this embodiment, at least one hollow sleeve extends downwardly between the two top cords of each web truss and rests upon the top surface of the bottom cord of the web truss. Each hollow sleeve is adapted to allow a fastener to pass through the hollow sleeve and into a hole formed through the bottom cord of the web truss in order to secure the web truss to a timber frame member such as a rafter. Once the fastener has passed through the sleeve and the head of the fastener is resting on the top surface of the bottom cord of the web truss, the sleeve is filled with insulation and plugged.
In an alternative embodiment of the present invention, individual pieces of wood or any other suitable material are used to support loads placed upon the roof panel. The individual pieces, which are preferably 2xc3x976 or 2xc3x978 pieces of wood but may be any size, will be referred to as spanners in this application. The spanners extend longitudinally along the length of the roof panel.
A plurality transversely extending upper and lower cords are secured to the spanners, the spanners being located between the upper and lower cords. The upper and lower cords extend in a transverse direction and therefore are perpendicular to the longitudinally extending spanners. At the ends of the upper and lower cords, connecting cords join the upper cords to the lower cords.
An inner sheathing is secured to the lower surfaces of the lower cords of the insulated roof panel with the vapor barrier of the present invention sandwiched between the lower cords and the inner sheathing. Similarly, an outer sheathing is secured to the upper surfaces of the upper cords of the panel.
As in the other embodiments, insulation is located between the vapor barrier and the outer sheathing. The insulation may be any type of insulation, but is preferably non-rigid insulation which does not require the use of urethane glues or other environmentally harmful products.
An insulation dam or border extends around the perimeter of the roof panel and confines the insulation. The insulation dam comprises a pair of opposed longitudinally extending side members or pieces and a pair of opposed transversely extending end members or pieces which define a cavity in which the insulation is located. The insulation dam is preferably made of four individual planar members, the side dam members of the insulation dam being secured to the connecting cords of the insulated roof panel and the end members of the dam being secured to outermost upper and lower cords of the insulated roof panel.
The insulation dam contains the insulation but allows air to flow over the top of the insulation and through the panel to properly vent the roof panel. The height of at least two of the insulation dam members is less than the height of the insulated roof panel and preferably equal to the distance from the inner sheathing to the top surface of the insulation. Thus a gap exists between the outer sheathing and the top surface of the insulation dam members, allowing air to flow over the insulation and vent moisture away from the insulation.
In each embodiment of the present invention, the roof panel provides strength to the overall building and transfers roof loads onto the timber frame members. These and other objectives and advantages of the present invention will be more readily apparent from the following description of the drawings: